Jackie, really? Right now, I don't have ANYTHING in the base font size field. I leave it blank, and, as I said, oftentimes (25% of the time or so), the font size in the main body of the text is something OTHER than 1em (which is what I find frustrating). Sometimes it's larger, sometimes smaller, thereby rendering my custom CSS different from the standard of 1em. Are you saying that if I put 12pt in the "Base Font Size" during the conversion, it will ALWAYS output 1em font size in the main body? I will test this when I get home with some of my problem conversions.

Are you saying that if I put 12pt in the "Base Font Size" during the conversion, it will ALWAYS output 1em font size in the main body? I will test this when I get home with some of my problem conversions.

That sounds correct. Since I have older eyes I use 16pt and end up consistently with 1.33em.

Jackie, really? Right now, I don't have ANYTHING in the base font size field. I leave it blank, and, as I said, oftentimes (25% of the time or so), the font size in the main body of the text is something OTHER than 1em (which is what I find frustrating). Sometimes it's larger, sometimes smaller, thereby rendering my custom CSS different from the standard of 1em. Are you saying that if I put 12pt in the "Base Font Size" during the conversion, it will ALWAYS output 1em font size in the main body? I will test this when I get home with some of my problem conversions.

I believe so, Japes, but my evidence is purely circumstantial (or do I mean anecdotal?). All my converted epubs end up with the body class font-size set to 1em when I use the following settings:

Nope. Doesn't work. I tested on a book with a font size of 1.29167em and, deleted the epub and reconverted (from Mobi...I have both the source and new files saved) using the 12pt base font size. When I opened up the new epub. Same font size of 1.29167em.

After further inspection I'm seeing font sizes of x-small or small or large on the source files (Mobi), for the main body, which is probably why it's going to a default of something OTHER than 1em for the main body. I don't have any idea why anyone would do that, but, it appears to be so.